Faster-Than-Light Discovery Raises Prospect of Time Travel

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If a report of particles traveling faster than the speed of light
turns out to be true, it will rock the foundations of modern
physics — and perhaps even change the way scientists think about
time travel.

But don't fire up the DeLorean just yet. Physicists are skeptical
that the
tiny subatomic particles, called neutrinos, really are
breaking the cosmic rule that nothing goes faster than light. And
even if they are, neutrinos don't make the best vessel for
sending signals to the past because they pass through ordinary
matter almost unaffected, interacting only weakly with the wider
world. [ Countdown
of Bizarre Subatomic Particles ]

So you may be able to send neutrinos back in time, but would
anyone notice? "If you're trying to get people's attention by
bouncing neutrinos off their head, you could wait for quite
awhile," Seth Lloyd, a physicist at the Massachusetts Institute
of Technology, told LiveScience.

That hasn't stopped physicists from imagining the possibilities
in a world where faster-than-light travel is possible. If the
neutrino experiment is confirmed, it opens the door to at least
sending messages through time using those neutrinos, physicists
say. You might even be able to send messages to "past you" with
neutrinos, one physicist suggests. Experiencing time backwards,
once thought impossible, might be outside the realm of sci-fi,
another imagines. Of course, this is all predicated on the
finding being true — and it raises thorny questions of how the
universe would work if people were able to go back in time and,
say, erase their own existence.

Physics shocker

The news that European researchers had detected neutrinos
traveling
faster than light broke yesterday (Sept. 22), triggering both
typical scientific skepticism and pure amazement in the physics
world. In an experiment that zaps neutrinos from CERN in Geneva
to the INFN Gran Sass Laboratory in Italy, scientists clocked the
particles outrunning light by 60 nanoseconds over 453.6 miles
(730 kilometers) — a neck-and-neck race to be sure. [ Infographic:
See How Neutrino Experiment Works ]

According to Einstein's Theory of Special Relativity, neutrinos
shouldn't even be able to match light speed, much less break it.
Neutrinos have (very small) mass, and as Einstein posited in his
famous E=mc squared equation, mass is equal to energy. As
something speeds up, its energy increases, too. Because energy is
equivalent to mass, its mass increases. Now you've got a heavier
object, so you've got to add even more energy to get it going
faster. Before you know it, you need "completely unreasonable"
amounts of energy to keep inching your object toward light speed,
said Harvard University physicist Gary Feldman.

"You keep accelerating but you just incrementally approach [light
speed], so you have to add more and more energy to go faster and
faster, but it becomes less and less effective," Feldman told
LiveScience.

Some particles have been shown to exceed the speed of light when
traveling in a medium rather than a vacuum, but neutrinos pass
through the Earth as if it were a vacuum, so they shouldn't ever
be able to
zip past light speed. The buzz in the physics community is
that they probably haven’t.

"Even though the experimenters have done a very careful job and
it's a very impressive paper … it was a very complicated analysis
and there's always a possibility that there's just an error in
what they did," Feldman said.

One possible error could be in the calculations the scientists
used to correct for the effect of the atmosphere in their
experiment, Lloyd said. Light actually gets a bit bogged down
when it isn't in a vacuum, while neutrinos zip through the
atmosphere without any effect. It's possible that the CERN
researchers miscalculated in correcting for the atmospheric
effect and that neutrinos aren't actually going faster, but the
light is just going a smidge slower than they realize.

If it's true ...

But if the results do hold, "it's major, it's humongous, it's the
biggest thing in 100 years," said Michio Kaku, a theoretical
physicist at the City University of New York.

"You're talking about a tidal wave hitting physics if it's true,"
Kaku told LiveScience. "There are two rocks upon which modern
physics is based. One is quantum theory and one is
relativity. If one of the pillars falls, we're in deep trouble."

What does that mean for time
travel ? In theory, it might be more possible than scientists
had thought. Einstein pointed out that time is relative: As you
approach light speed, your experience of time is not the same as
it is for the folks chugging along at their usual speed. What
feels like a second to you will feel like much longer to them.
This idea, called "time dilation," spawned such sci-fi classics
as 1968's "Planet of the Apes," in which what feels like 18
months to Charleton Heston and his crew is enough time for
gorillas, chimps and orangutans to evolve language and complex
societies back on Earth. [ Top
10 Scary Sci-Fi Series ]

There are a lot of barriers to approaching light speed, much less
breaking it, but if you could, you could theoretically experience
time running backward, Kaku said. Here's how it would work: As
you approach light speed, you might time goes slower in the
outside world than it does for you. When you hit light speed, the
outside world goes so slow in relation to you that it stops
(again, in relation to you; people in the outside world feel as
if time is the same as always). So if you could push past that
speed limit, the outside world would be so slow as to be moving
backward in relation to you.

So far, this seems pretty much impossible, not least because some
other side effects of faster-than-light travel should include
reducing your weight and width to less than nothing, Kaku said.
[Watch: Can You Time
Travel? ]

If the neutrinos are actually going faster than light, though, it
might be possible to use them to communicate with the past, Lloyd
said. You could send off a faster-than-light message to someone
moving at a rapid velocity with respect to you. They could then
bounce the faster-than-light message back, and it would arrive
before the signal you sent to them.

One way to think of this is like a mirror, Lloyd said. You send a
message to the mirror, and it reflects it back, but so quickly
that "past you" is the one who receives it.

But all of this is moot if it's only neutrinos that can be coaxed
past the speed of light, Lloyd said. Because they don't interact
with much, your messages would likely go unnoticed by past
generations. An April 13, 1865, warning to Abraham Lincoln not to
go into Ford's Theater the next day would pass through the
president like a ghost. [Read:
'Time Traveler' Spotted? ]

Doing away with Einstein's theory would also complicate
causality, the idea that things influence each other in
chronological order. When you allow the past, present and future
to interact, "that gets all messed up," Lloyd said, and you
start
to get paradoxes. A classic is the Grandfather Paradox: What
if you went back in time and shot your grandfather, preventing
your own birth and thus preventing yourself from ever shooting
your grandfather?

It's a headache, to say the least. And not all researchers are
convinced that the finding, even if true, would ultimately
overturn the well-tested, century-old Special Theory of
Relativity that keeps things from getting so messy.

"This effect is very small, it's two parts in 100,000," Feldman
said. "If this is true, what it means is that there is some
aspect of the Special Theory of Relativity that's been overlooked
or not understood well, but I can't imagine that it really
overtakes the Special Theory of Relativity."